Fuel resistance package

ABSTRACT

A fuel resistance package includes a member to be sealed, which is used in a fuel atmosphere including an aromatic compound or ethanol, and a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere. The sealing member is made of resin containing glycidyl amine-based epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less as epoxy resin, an amine-based hardener that ring-opens epoxy groups of the epoxy resin to harden the epoxy resin, and filler made of silica.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on Japanese Patent Application No.2009-283719 filed on Dec. 15, 2009, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fuel resistance package having amember to be sealed, which is used in a fuel atmosphere including anaromatic compound or ethanol, and a sealing member, which seals themember to be sealed so that the member to be sealed is protected fromfuel in the fuel atmosphere.

BACKGROUND OF THE INVENTION

Environment resistance and, especially, high reliability are requiredfor a package that is directly exposed to fuel or the like. In order tofulfill the reliability, a configuration, in which a member to be sealedis sealed with a sealing member made of inorganic material, hasconventionally adopted. As a fuel resistance package having such aconfiguration, a pressure sensor described in JP-A-7-209115 hasproposed, for example.

In the package, a metal diaphragm made of inorganic material andtransmitting oil are used as the sealing member, and a sensor element ora wiring part as the member to be sealed is sealed with the metaldiaphragm and the transmitting oil, thereby improving the environmentresistance.

However, in the package described in JP-A-7-209115, the followingproblems arise. Since the metal diaphragm is used, material cost mayincrease. Since control of voids in the enclosed oil is required, laborcost may increase. Since many components are needed, reducing a size ofthe package may become so difficult.

In view of the above-described problems, the inventors considered usingresin material as the sealing member having fuel resistance in place ofthe conventional inorganic material. However, in the case where resinmaterial is used, components in fuel, such as an aromatic compound orethanol may penetrate the sealing member, and thereby fuel resistance ofthe sealing member may be decreased. Therefore, in the case where theresin material is used as the sealing member, prevention of thepenetration of the components is needed.

SUMMARY OF THE INVENTION

In view of the above-described difficulty, it is an object of thepresent invention to provide a fuel resistance package having a memberto be sealed, which is used in a fuel atmosphere including an aromaticcompound or ethanol, and a sealing member, which seals the member to besealed so that the member to be sealed is protected from fuel in thefuel atmosphere, and being capable of preventing components in the fuelfrom penetrating the sealing member.

In order to achieve the above-described object, the inventors consideredthat molding resin used as a sealing member in a semiconductor device orthe like is improved to be a sealing member suitable for a fuelresistance package.

This kind of molding resin includes resin containing epoxy resin as amajor component and a hardener that ring-opens epoxy groups of the epoxyresin to harden the epoxy resin, filler made of silica, and a couplingagent for ensuring a binding property between the filler and the epoxyresin.

The inventors analyzed a glass-transition temperature of epoxy resin,and affinity of epoxy resin for components in fuel, such as an aromaticcompound or ethanol. It is considered that, when the glass-transitiontemperature is low, a sealing member is easy to be softened, and itbecomes easy to form voids in the sealing member microscopically, andthus, the components in the fuel become easy to penetrate the sealingmember.

A relation between the glass-transition temperature of epoxy resin inthe sealing member and a penetration degree of the components in thefuel was experimentally analyzed by using NMR. According to theanalysis, it was found that, when the glass-transition temperature is180° C. or more, penetration of the components in the fuel can belimited at a practical level.

Moreover, the inventors thought that it is preferable that a dielectricconstant of the epoxy resin in the sealing member is low in order toprevent penetration of ethanol as polar solvent among the components inthe fuel. This is because, if the dielectric constant is large, affinityof the epoxy resin for a hydroxyl group (—OH) of ethanol becomes largeand ethanol penetrates easily.

A relation between the dielectric constant of the epoxy resin in thesealing member and the penetration degree of the components in the fuelwas experimentally analyzed. As shown in FIGS. 3A and 3B, which aredescribed below, it was found that, when the dielectric constant is 3.5or less, the penetration of ethanol in the fuel can be limited at apractical level.

According to one aspect of the present invention, a fuel resistancepackage includes a member to be sealed, which is used in a fuelatmosphere including at least one of an aromatic compound and ethanol,and a sealing member, which seals the member to be sealed so that themember to be sealed is protected from fuel in the fuel atmosphere. Thesealing member is made of resin containing epoxy resin having aglass-transition temperature of 180° C. or more and a dielectricconstant of 3.5 or less, and filler made of silica is contained in theresin.

The sealing member of the present invention is made of resin containingepoxy resin having a glass-transition temperature of 180° C. or more anda dielectric constant of 3.5 or less, and filler made of silica iscontained in the resin. Therefore, even if a sealing member made ofresin material is used, components in fuel can be prevented frompenetrating the sealing member.

Furthermore, in order to prevent penetration of an aromatic compoundamong the components in the fuel, it is preferable that the affinity ofthe epoxy resin in the sealing member for the aromatic compound is low.A planar space in a molecule is large in naphthalene-based epoxy resin,for example. Thus, the affinity of the naphthalene-based epoxy resin foran aromatic compound having a benzene ring becomes large, and thearomatic compound penetrates easily.

With focusing this point, a relation between a molecular structure ofthe epoxy resin in the sealing member and the penetration degree of thecomponents in the fuel was experimentally analyzed. As a result, it wasfound that, when glycidyl amine-based epoxy resin whose planar space issmaller than that of naphthalene-based epoxy resin is used, thepenetration of the aromatic compound in the fuel can be limited.

In the case of using the glycidyl amine-based epoxy resin, a hardenerthat ring-opens epoxy groups of the epoxy resin to harden the epoxyresin was analyzed. In general molding resin, examples of the hardenerinclude an amine-based hardener such as imidazole, a phenol-basedhardener and an anhydride-based hardener.

The inventors intended to form the sealing member as follows. Liquidmaterial for the sealing member is applied to the member to be sealed bypotting or the like, and then, the applied liquid material is hardened.Since viscosity of a phenol-based hardener becomes high in the step ofapplying, the inventors decided not to use a phenol-based hardener.

Then, the inventors analyzed an amine-based hardener and ananhydride-based hardener, each of which has a relatively-low viscosity,and focused adhesion force between a sealing member and a member to besealed in order to select a preferred hardener. It is considered thatthe adhesion force between the sealing member and the member to besealed is affected significantly by a hydrogen bond due to the hydroxylgroup (—OH) of the resin of the sealing member.

In using the amine-based hardener and the anhydride-based hardener, aring-opening rate of glycidyl amine-based epoxy resin was experimentallyanalyzed. As a result, the ring-opening rate is considerably large whenthe amine-based hardener is used compared to when the anhydride-basedhardener is used.

Furthermore, with respect to the sealing member made of the glycidylamine-based epoxy resin, interfacial strengths with the member to besealed when the amine-based hardener is used and when theanhydride-based hardener is used were experimentally analyzed. As aresult, as shown in FIG. 5, which is described below, it was found that,the adhesion force between the sealing member and the member to besealed is substantially large when the amine-based hardener is usedcompared to when the anhydride-based hardener is used.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a schematic cross-sectional view showing a fuel resistancepackage according to a first embodiment of the present invention;

FIG. 2A is a diagram showing a molecular structure of naphthalene-basedepoxy resin;

FIG. 2B is a diagram showing a molecular structure of glycidylamine-based epoxy resin;

FIG. 3A is a graph showing a relation between immersion time and masschange in the case where naphthalene-based epoxy resin is used;

FIG. 3B is a graph showing a relation between immersion time and masschange in the case where glycidyl amine-based epoxy resin is used;

FIG. 4A is a graph showing a relation between immersion time and masschange in the case where a filler content is 60% by weight;

FIG. 4B is a graph showing a relation between immersion time and masschange in the case where a filler content is 80% by weight;

FIG. 5 is a graph showing a relation between immersion time andinterfacial strength in the case where an amine-based hardener is usedand in the case where an anhydride-based hardener is used;

FIG. 6 is a graph showing a relation between immersion time and breakingstress of a sealing member;

FIG. 7 is a schematic cross-sectional view showing a substantial part ofa fuel resistance package according to a second embodiment of thepresent invention;

FIG. 8 is a schematic cross-sectional view showing a fuel resistancepackage according to a third embodiment of the present invention;

FIG. 9 is a schematic cross-sectional view showing a fuel resistancepackage according to a fourth embodiment of the present invention; and

FIG. 10 is a schematic cross-sectional view showing a fuel resistancepackage according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to drawings. For the sake of simplicity, similar components inthe following embodiments are indicated by the same reference numeral.

First Embodiment

FIG. 1 is a schematic cross-sectional view showing a fuel resistancepackage S1 according to the first embodiment of the present invention.As shown in FIG. 1, the package S1 is used in a fuel atmosphere 1containing an aromatic compound or ethanol, and is applied as varioussensor devices which are mounted to a vehicle. Examples of the fuelinclude gasoline containing an aromatic compound or ethanol, that is,deteriorated gasoline.

Generally, the package S1 of the present embodiment includes a sensorchip 10, a first substrate 20 that supports the sensor chip 10, a wire30 that electrically connects the sensor chip 10 and the first substrate20, and a second substrate 40 that supports the first substrate 20.

Examples of the sensor chip 10 include a pressure sensor, anacceleration sensor, a flow sensor, or a temperature sensor. Forexample, the sensor chip 10 is a semiconductor chip that is formed by asemiconductor process. Each of the first substrate 20 and the secondsubstrate 40 is a wiring substrate or a lead frame, for example.

The sensor chip 10 is mounted on and fixed to one surface of the firstsubstrate 20 by an adhesive 50 such as solder or Ag paste, and thereby,the sensor chip 10 is supported by the first substrate 20. The sensorchip 10 is placed on one end portion of the first substrate 20 such thata part of the sensor chip 10 protrudes from the one end portion of thefirst substrate 20.

The sensor chip 10 is wire-connected to the first substrate 20 with thewire 30 made of aluminum, gold or the like at a side of the one endportion of the first substrate 20, and thereby the sensor chip 10 iselectrically connected to the first substrate 20. The wire 30 is formedby wire bonding, for example.

The other end portion of the first substrate 20 is mechanically joinedto one end portion of the second substrate 40. Although not shown, thejoining is performed by using an adhesive such as solder, or a screw, orby caulking, for example. The first and second substrates 20, 40 contacteach other through electrodes thereof (not shown). Thus, the firstsubstrate 20 is electrically joined to the second substrate 40.

A resin-molded first resin portion 61 is placed on the one surface ofthe first substrate 20. The first resin portion 61 covers the onesurface of the first substrate 20 other than the sensor chip 10 and thewire 30. A part of the first substrate 20 including the first resinportion 61 and a part of the second substrate 40 are sealed with aresin-molded second resin portion 62.

The second resin portion 62 seals the first and second substrates 20, 40so as to surround a joined portion between the first and secondsubstrates 20, 40, the first and second substrates 20, 40 which arelocated adjacent to the joined portion, and a part of the first resinportion 61. The sensor chip 10, the wire 30, a part of the firstsubstrate 20 on which the sensor chip 10 and the wire 30 are placed, andthe other end portion of the second substrate 40 protrude from thesecond resin portion 62.

The first resin portion 61 is made of epoxy resin, and the second resinportion 62 is made of PPS (polyphenylene sulfide), for example. Thefirst and second resin portions 61, 62 are formed by transfer moldingwith the use of a molding die. After the first resin portion 61 isprimary molded, the second resin portion 62 is secondary molded so as tobe in contact with the first resin portion 61.

According to the present embodiment, in such a package S1, the sensorchip 10 corresponds to a first member, the first substrate 20corresponds to a second member, and the wire 30 corresponds to aconnecting member that electrically connects the first and secondmembers. As shown in FIG. 1, the wire 30, and the first and secondmembers which are located adjacent to the wire 30 are sealed by asealing member 70.

In the present embodiment, a boundary portion at which the first resinportion 61 contacts the second resin portion 62 is also sealed with thesealing member 70. Furthermore, the sealing member 70 also seals tocover a boundary portion that becomes a boundary outside the first andsecond resin portions 61, 62 on an outer peripheral surface of the firstand second resin portions 61, 62.

Accordingly, in the package S1, a portion 71 other than the sealingmember 70 in the package S1, that is, the portion 71 composed of thesensor chip 10, the first and second substrates 20, 40, the wire 30, theadhesive 50 and the first and second resin portions 61, 62 correspondsto a member 71 to be sealed. When the package S1 is used, the componentslocated in the fuel atmosphere 1 of the member 71 to be sealed, that is,the wire 30, adjacent parts to the wire 30 and the boundary portion aresealed with the sealing member 70.

The sealing member 70 is made of resin material containing filler, andcan limit the penetration of components in the fuel as much as possible.Unlike the first and second resin portions 61, 62, the sealing member 70is not formed by molding with the use of the molding die. The sealingmember 70 is formed as follows. Liquid material for the sealing member70 is applied to the member 71 to be sealed by potting or the like, andthen, the applied liquid material is hardened. Portions that are easy tobe deteriorated due to the fuel of the member 71 to be sealed are sealedwith the sealing member 70, and thereby the member 71 to be sealed isprotected from the fuel.

In particular, the sealing member 70 is made of resin containing epoxyresin and filler made of silica contained in the resin. The resincontaining epoxy resin includes the epoxy resin as a major component, ahardener that ring-opens epoxy groups of the epoxy resin to harden theepoxy resin, and a coupling agent for ensuring a binding propertybetween the filler and the epoxy resin.

The epoxy resin having a glass-transition temperature of 180° C. or moreand a dielectric constant of 3.5 or less is used. Examples of the epoxyresin include polycyclic epoxy resin. In particular, it is preferable touse glycidyl amine-based epoxy resin as resin that can achieve the highglass-transition temperature and the low dielectric constant and is easyto limit the penetration of aromatic components in the fuel.

Examples of the hardener include an amine-based hardener. It ispreferable to use the amine-based hardener since adhesion force, i.e.,interfacial strength between the sealing member 70 and the member 71 tobe sealed is increased. Furthermore, an epoxy-based coupling agent whichis the same with general molding resin that is used as a sealing memberin a semiconductor device, is used as the coupling agent, and the amountthereof is the same with that of the molding resin.

Particulate silica which is the same with that contained in generalmolding resin is used as the filler. When the whole of the sealingmember 70 is assumed to be 100% by weight, it is preferable that theamount of the filler is 60% by weight or more, more preferably, 80% byweight. The above-described configuration of the sealing member 70 isbased on an experimental result by the inventors, and the experimentalresult used as the basis for the configuration will be described below.

As described above, the package S1 of the present embodiment is used inthe fuel atmosphere 1 such as the deteriorated gasoline containing anaromatic compound or ethanol. In particular, the package S1 is used as asensor for measuring a pressure or a temperature in a fuel tank of thevehicle.

According to FIG. 1, the sensor chip 10, the wire 30, the firstsubstrate 20, and the first resin portion 61, and a part of the secondresin portion 62 are used in the fuel atmosphere 1. The other endportion of the second substrate 40 protruding from the second resinportion 62 is located outside the fuel atmosphere 1. In this state, asignal from the sensor chip 10 is outputted to the outside from theother end portion of the second substrate 40 through the wire 30 and thefirst and second substrates 20, 40.

When the package S1 is used, the components in the member 71 to besealed, which are located in the fuel atmosphere 1 and should beprotected from the fuel, are sealed with the sealing member 70. Sincethe sealing member 70 can limit the penetration of components in thefuel, such as an aromatic compound or ethanol as much as possible, thedeterioration of the member 71 to be sealed due to the fuel can beprevented.

In the present embodiment, since the boundary portion between the firstand second resin portions 61, 62 is sealed with the sealing member 70,the sealing member 70 fulfills a function to increase joint strengthbetween the first and second resin portions 61, 62.

In the package S1 of the present embodiment, the case where the fuelresistance of the boundary portion between the first and second resinportions 61, 62 is unnecessary depending on composition or a temperaturein the fuel atmosphere is assumed. In such a case, the sealing member 70may not be formed on the boundary portion in the above-describedconfiguration. Next, the effect of the sealing member 70 of the presentembodiment and the basis that the sealing member 70 is formed to havethe above-described configuration will be specifically described.

First, the reason why the glass-transition temperature of the epoxyresin in the sealing member 70 is set to be 180° C. or more will bedescribed. An immersion test was performed by using epoxy resin havingthe glass-transition temperature of less than 100° C. and epoxy resinhaving the glass-transition temperature of 180° C. as the sealing member70. In the immersion test, the two types of epoxy resins are immersed inthe deteriorated gasoline having a temperature of 80° C. for 1000 hours,and NMR measurement of the epoxy resins was performed before and afterthe immersion. Increase and decrease of peaks due to an aromaticcompound and ethanol in the deteriorated gasoline were analyzed based onthe NMR spectra.

As a result, in the epoxy resin having the glass-transition temperatureof less than 100° C., the peaks due to both the aromatic compound andethanol were increased after the immersion. In contrast, in the epoxyresin having the glass-transition temperature of 180° C., the peaks dueto both the aromatic compound and ethanol were not increased.

That is, it was found that the epoxy resin having the glass-transitiontemperature of 180° C. substantially limits the penetration of thearomatic compound and ethanol. Therefore, if the glass-transitiontemperature of the epoxy resin of the sealing member 70 is 180° C. ormore, the sealing member 70 becomes hard, and the penetration of thecomponents in the fuel can be limited.

Next, as epoxy resin having the glass-transition temperature of 180° C.or more, the case where naphthalene-based epoxy resin is used and thecase where glycidyl amine-based epoxy resin is used were compared, andhardening thereof due to the difference between the dielectric constantsand molecular structures thereof was analyzed. In particular, thesealing member including naphthalene-based epoxy resin and the sealingmember including glycidyl amine-based epoxy resin were immersed in thedeteriorated gasoline having a temperature of 80° C., and a relationbetween the immersion time and the mass change of the sealing member wasobtained.

FIG. 2A is a diagram showing a molecular structure of naphthalene-basedepoxy resin, which is used in the analysis. FIG. 2B is a diagram showinga molecular structure of glycidyl amine-based epoxy resin, which is usedin the analysis. The dielectric constant of the naphthalene-based epoxyresin is 3.8, and the dielectric constant of the glycidyl amine-basedepoxy resin is 3.5.

FIG. 3A is a graph showing the relation between the immersion time(unit: hour) and the mass change (unit: %) in the case where thenaphthalene-based epoxy resin is used. FIG. 3B is a graph showing therelation between the immersion time (unit: hour) and the mass change(unit: %) in the case where the glycidyl amine-based epoxy resin isused. In FIGS. 3A and 3B, the mass change is expressed in percentagebased on the immersion time 0, that is, the mass of the sealing memberbefore the immersion.

As shown in FIGS. 3A and 3B, in both cases, the mass of the sealingmember increases with immersion time. The mass of the sealing memberincreases because components of an aromatic compound or ethanol in thedeteriorated gasoline penetrate the sealing member and the sealingmember swells. That is, it can be said that the lower the degree of themass increase is, the better the penetration of the components issuppressed.

In particular, as shown in FIGS. 3A and 3B, in the case of usingnaphthalene-based epoxy resin, the mass increase was 1.5% after theimmersion of 1000 hours, and in the case of using glycidyl amine-basedepoxy resin, the mass increase was 0.7% after the immersion of 1000hours. 0.7% is a value that practically realizes sufficient fuelresistance in this kind of package.

According to the analysis, it appears that, if the dielectric constantof the epoxy resin of the sealing member 70 is 3.5 or less, thepenetration of the ethanol component in the fuel can be limited at apractical level. The reason is as follows. If the dielectric constant islow, for example, 3.5 or less, it is presumed that affinity of the epoxyresin for a hydroxyl group (—OH) of ethanol as polar solvent becomessmall and the penetration of ethanol is drastically suppressed.

Moreover, in the case of using glycidyl amine-based epoxy resin, thepenetration of the aromatic component in the fuel is also drasticallysuppressed compared with the case of using naphthalene-based epoxyresin, which is presumed to be dependent on the difference between themolecular structure of naphthalene-based epoxy resin and the molecularstructure of glycidyl amine-based epoxy resin.

As shown in FIGS. 2A and 2B, a planar space of benzene rings innaphthalene-based epoxy resin is large, and a planar space of benzenerings in glycidyl amine-based epoxy resin is small. Thus, the affinityfor an aromatic component having a benzene ring in glycidyl amine-basedepoxy resin is smaller than that in naphthalene-based epoxy resin, andthereby it is considered that the penetration of the aromatic componentdoes not take place easily in the case of using glycidyl amine-basedepoxy resin.

Next, a filler content will be described. If a resin component in thesealing member 70 made of resin is too much, the penetration amount ofthe components in the fuel may increase. Thus, it is considered that thepenetration amount of the components in the fuel can be limited byincreasing the filler content to some extent to decrease the resincomponent in the sealing member 70. A relation between the fillercontent and the penetration degree of the components in the fuel wasexperimentally analyzed.

In the analysis, the sealing member made of resin containing glycidylamine-based epoxy resin having the glass-transition temperature of 180°C. or more and the dielectric constant of 3.5 or less is used. Theamount of filler that is contained in the resin was changed. Withrespect to the sealing members whose filler contents vary from eachother, each sealing member was immersed in the deteriorated gasolinehaving a temperature of 80° C., and a relation between the immersiontime and the mass change of the sealing member was obtained. The resultis shown in FIGS. 4A and 4B.

FIG. 4A is a graph showing the relation between the immersion time(unit: hour) and the mass change (unit: %) in the case where the fillercontent is 60% by weight. FIG. 4B is a graph showing the relationbetween the immersion time (unit: hour) and the mass change (unit: %) inthe case where the filler content is 80% by weight.

As shown in FIG. 4A, in the case where the filler content is 60% byweight, the penetration degree of the components in the fuel slightlyexceeds 1%, and the resin having the filler content of 60% by weight canbe barely used at a practical level although depending on a fuelatmosphere. Moreover, as shown in FIG. 4B, in the case where the fillercontent is 80% by weight, the penetration degree of the components inthe fuel is drastically improved compared to the case where the fillercontent is 60% by weight. Accordingly, it is preferable that the fillercontent is 60% by weight, and more preferably, is 80% by weight.

As the hardener for obtaining moderate low viscosity in the step ofapplying the sealing member 70, the amine-based hardener and theanhydride-based hardener, which have relatively low viscosity, wereselected and compared to each other with focusing the adhesion forcebetween the sealing member 70 and the member 71 to be sealed. It isconsidered that the adhesion force is affected significantly by ahydrogen bond due to the hydroxyl group (—OH) of the resin of thesealing member 70. In using the respective hardeners, a ring-openingrate of glycidyl amine-based epoxy resin was analyzed.

In the analysis, with respect to the sealing member containing theamine-based hardener as the hardener for the glycidyl amine-based epoxyresin and the sealing member containing the anhydride-based hardener asthe hardener for the glycidyl amine-based epoxy resin, NMR measurementwas performed before and after hardening. The ring-opening rates of theglycidyl amine-based epoxy resins in the sealing members were measuredbased on the NMR spectra. As a result, the ring-opening rate when usingthe amine-based hardener was about 70%. In contrast, the ring-openingrate when using the anhydride-based hardener was about 20%. That is, thering-opening rate is considerably large when using the amine-basedhardener compared to when using the anhydride-based hardener.

Furthermore, in the sealing member 70 in which the resin containing theglycidyl amine-based epoxy resin shown in FIG. 2B and the filler contentis 80% by weight, the interfacial strengths with the member 71 to besealed when the amine-based hardener is used and when theanhydride-based hardener is used were analyzed.

In the analysis, each sealing member 70 was immersed in the deterioratedgasoline having a temperature of 80° C., and a relation between theimmersion time and the interfacial strength was obtained. The materialfor the sealing member 70 was applied to the plate-like member to besealed and hardened so that the sealing member 70 having a pudding cupshape was formed. The interfacial strength was measured by a test formeasuring shear strength with respect to the above sealing member 70,i.e., a pudding cup test. The result is shown in FIG. 5.

FIG. 5 is a graph showing the relation between the immersion time andthe interfacial strength in the case where the amine-based hardener isused and in the case where the anhydride-based hardener is used. Thewhite rhombus plots in FIG. 5 show the case where the amine-basedhardener is used, and the black rhombus plots in FIG. 5 show the casewhere the anhydride-based hardener is used.

The plots in FIG. 5 surrounded by broken line circles show shearstrength when the member to be sealed itself fractures and a fracture ata boundary portion between the sealing member and the member to besealed does not occur, i.e., interfacial strength of “cohesion failureof the member to be sealed”. The plots in FIG. 5 surrounded by solidline circles show shear strength when a fracture at the boundary portionoccurs, i.e., interfacial strength of “interface failure”.

As shown in FIG. 5, the interfacial strength is drastically decreasedwhen the anhydride-based hardener is used compared to when theamine-based hardener is used. The result directly reflects thedifference of the ring-opening rate, and eventually, the difference ofthe adhesion force with the member to be sealed between the amine-basedhardener and the anhydride-based hardener. Accordingly, it was decidedto use the amine-based hardener as the hardener.

The inventors analyzed mechanical strength of the sealing member 70. Thesealing member 70 includes resin containing the glycidyl amine-basedepoxy resin having the glass-transition temperature of 180° C. and thedielectric constant of 3.5 as epoxy resin and the amine-based hardener,and the filler. The filler content is 80% by weight.

In the analysis, the sealing member 70 that is hardened to have adumbbell shape, was immersed in the deteriorated gasoline having atemperature of 80° C., and a relation between the immersion time and themechanical strength was measured. Here, the mechanical strength wasobtained as follows. Tension is applied to the sealing member 70 havingthe dumbbell shape, and stress when the sealing member 70 is broken,that is, breaking stress was obtained as the mechanical strength. Theresult is shown in FIG. 6.

FIG. 6 is a graph showing the relation between the immersion time (unit:hour) and the breaking stress (unit: MPa). As shown in FIG. 6, themechanical strength of the sealing member 70 of the present embodimenthardly changed even if the sealing member 70 was exposed to the fuelatmosphere. That is, the sealing member 70 has a great fuel resistanceproperty.

As described above, according to the present embodiment, the sealingmember 70 is made of glycidyl amine-based epoxy resin having theglass-transition temperature of 180° C. or more and the dielectricconstant of 3.5 or less, the amine-based hardener that ring-opens epoxygroups of the epoxy resin to harden the glycidyl amine-based epoxyresin, and the filler made of silica. Therefore, even if the sealingmember 70 made of resin material is used, components in fuel, such as anaromatic compound or ethanol can be prevented from penetrating theinside of the sealing member 70.

Second Embodiment

FIG. 7 is a schematic cross-sectional view showing a substantial part ofa fuel resistance package according to the second embodiment of thepresent invention. In the present embodiment, an object to be sealed bythe sealing member 70 is different from that in the first embodiment,and the different point will be mainly described.

As shown in FIG. 7, the package of the present embodiment has a bump 31in place of the wire 30 as the connecting member, which electricallyconnects the sensor chip 10 and the first substrate 20 that supports thesensor chip 10. The bump 31 is a general bump made of gold, copper orthe like.

According to the present embodiment, in the configuration shown in FIG.7, a part 72 other than the sealing member 70, that is, the part 72composed of the sensor chip 10, the first substrate 20 and the bump 31corresponds to a member 72 to be sealed. In the member 72 to be sealed,the sealing member 70 is placed between the sensor chip 10 and the firstsubstrate 20, and seals the bump 31.

In this case, the sealing member 70 also has a function as an underfillmember below the sensor chip 10, and it is desirable to decreasesomewhat the filler content compared to the sealing member 70 of thefirst embodiment.

Third Embodiment

FIG. 8 is a schematic cross-sectional view showing a fuel resistancepackage according to the third embodiment of the present invention. Asshown in FIG. 8, the package of the present embodiment is different fromthe package S1 of the first embodiment (refer to FIG. 1) in that thewire 30 and the sensor chip 10 that is located adjacent to the wire 30are sealed by the first resin portion 61 not the sealing member 70.

Here, a member 73 to be sealed in the present embodiment corresponds toa part other than the sealing member 70 in the configuration shown inFIG. 8. That is, as with the package S1 of the first embodiment, in thepresent embodiment, the member 73 to be sealed includes the first resinportion 61 that is primary molded and the second resin portion 62 thatis secondary molded and located to be in contact with the first resinportion 61, and the boundary portion between the first and second resinportions 61, 62 is sealed by the sealing member 70.

As described above, the sealing member 70 may seal only the boundaryportion at which the first resin portion 61 contacts the second resinportion 62. In this case, by using the sealing member 70, the fuelresistance property at the boundary portion and increasing of the jointstrength at the boundary portion can be obtained.

Fourth Embodiment

FIG. 9 is a schematic cross-sectional structure showing a fuelresistance package according to the fourth embodiment of the presentinvention. In the present embodiment, an object to be sealed by thesealing member 70 is different from that in the first embodiment.

As shown in FIG. 9, in the package of the present embodiment, a circuitchip 11 is mounted to the one surface of the first substrate 20 throughthe adhesive 50, and the circuit chip 11 is connected to the firstsubstrate 20 through the adhesive 50. Furthermore, the circuit chip 11is wire-connected to the one surface of the first substrate 20 with thewire 30, and thereby the circuit chip 11 is electrically connected tothe first substrate 20.

In this case, a member 74 to be sealed is composed of the components inFIG. 9 other than the sealing member 70, that is, the circuit chip 11,the first substrate 20 and the wire 30. In the present embodiment, thewhole circuit chip 11 and the whole wire 30 are used in the fuelatmosphere 1, and the sealing member 70 seals to surround the wholecircuit chip 11 and the whole wire 30 at a side of the one surface ofthe first substrate 20.

When the package is used, the circuit chip 11 and the wire 30 in themember 74 to be sealed, which are located in the fuel atmosphere 1 andneed the fuel resistance property, are sealed with the sealing member70. Therefore, the deterioration of the circuit chip 11 and the wire 30due to the fuel can be prevented.

Fifth Embodiment

FIG. 10 is a schematic cross-sectional structure showing a fuelresistance package according to the fifth embodiment of the presentinvention. In the package of the present embodiment, a member 75 to besealed is composed of the second substrate 40 that is connected to thefirst substrate 20, the first resin 61 that seals the whole circuit chip11 and the whole wire 30 on the one surface of the first substrate 20,and the second resin portion 62 that seals a part of the first resinportion 61 and a part of the first and second substrates 20, 40, inaddition to the components in FIG. 9 such as the circuit chip 11, theadhesive 50, the first substrate 20 and the wire 30.

The sealing member 70 seals the boundary portion at which the firstresin portion 61 contacts the second resin portion 62 in the member 75to be sealed. According to the present embodiment, by using the sealingmember 70, the fuel resistance property at the boundary portion andincreasing of the joint strength at the boundary portion can beobtained.

Other Embodiments

Epoxy resin in the sealing member 70 is not limited to the glycidylamine-based epoxy resin shown in the above embodiments as long as theepoxy resin has the glass-transition temperature of 180° C. or more andthe dielectric constant of 3.5 or less. For example, the epoxy resin maybe polycyclic epoxy resin other than the glycidyl amine-based epoxyresin.

As long as the member to be sealed includes the first member, the secondmember and the connecting member that electrically connects the firstand second members, and the connecting member is sealed with the sealingmember, the above components are not limited to the sensor chip 10, thecircuit chip 11, the first substrate 20, the wire 30 and the bump 31.For example, both the first and second members may be chips, circuitboards or the like, and the connecting member may be a tape-like leadmember.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments and constructions. The invention isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, which arepreferred, other combinations and configurations, including more, lessor only a single element, are also within the spirit and scope of theinvention.

1. A fuel resistance package comprising: a member to be sealed, which isused in a fuel atmosphere including at least one of an aromatic compoundand ethanol; and a sealing member, which seals the member to be sealedso that the member to be sealed is protected from fuel in the fuelatmosphere, wherein the sealing member is made of resin containing epoxyresin having a glass-transition temperature of 180° C. or more and adielectric constant of 3.5 or less, and filler made of silica iscontained in the resin.
 2. The fuel resistance package according toclaim 1, wherein the epoxy resin is glycidyl amine-based epoxy resin,and the sealing member further includes an amine-based hardener thatring-opens an epoxy group of the glycidyl amine-based epoxy resin toharden the glycidyl amine-based epoxy resin.
 3. The fuel resistancepackage according to claim 1, wherein the member to be sealed includes:a first member; a second member; and a connecting member thatelectrically connects the first member and the second member, and theconnecting member is sealed with the sealing member.
 4. The fuelresistance package according to claim 1, wherein the member to be sealedincludes: a first resin portion that is primary molded; and a secondresin portion that is secondary molded and located to be in contact withthe first resin portion, and a boundary portion between the first resinportion and the second resin portion is sealed with the sealing member.5. The fuel resistance package according to claim 4, wherein the memberto be sealed further includes: a first member; a second member; and aconnecting member that electrically connects the first member and thesecond member, and the connecting member is sealed with the first resinportion.
 6. The fuel resistance package according to claim 2, whereinthe sealing member further includes a coupling agent that ensures abinding property between the filler and the glycidyl amine-based epoxyresin.